Aluminum brightener compositions



United States Patent ALUMINUM BRIGHTENER COMPOSITIONS Daniel R. KellWyandotte, Mich., assign'or to Wyandotte Chemicals Corporation,Wyandotte, Mich., a corporation of Michigan No Drawing. Filed Oct. 13,1958, Ser. No. 766,721 18 Claims. (Cl. 4142) This invention relates toways and means for brightening aluminum surfaces of articles such as thewings of aircraft. More particularly, it relates to aluminum brightenercompositions based on methylcellulose as a thickener.

In the manufacture and use of articles'h'aving aluminum surfaces(including aluminum alloy surfaces), such as those found, for example,on aircraft, such surfaces become discolored, tarnished and covered withcorrosion and oxidation products. For at least aesthetic reasons, it isdesirable in many cases to remove such tarnish and corrosion productsand discoloration, and otherwise brighten the surface of the aluminumarticle. A less obvious reason for removing such products of corrosionand oxidation resides in the fact that frequently cleaned aluminumsurfaces tend to last longer than infrequently cleaned aluminumsurfaces, or, to state it another way, in the fact that corrosion tendsto beget corrosion. Consequently, the removal of corrosion products fromaluminum articles upon completion of manufacturing operations has becomea standard finishing step and the 2,942,955 Patented June 28, 1960 icelong distances from the point of use from supplying these solutions atreasonable prices to users. Moreover, because the storage life of suchsolutions is limited, users are not able to purchase such solutions inlarge quantities. Consequently, up to the time of this invention, it hasbeen customary to prepare the solution only in such quantities as willbe used immediately and to do so at or near the place of use.

The aluminum brightener solutions developed heretofore by the art alsosuffer from another deficiency in that they are corrosive to magnesiumand magnesium In many instances, the removal of corrosion productshowever, it is unwieldy and impractical to dip or immerse the same intobaths. Accordingly, it is customary in the aircraft industry to brushorspray the brightener solution on the aluminum surfaces to bebrightened and, when the desired degree of brightening has occurred,

prevent run-off and subsequent streaking of vertically disposedsurfaces, the brightener solution under these conditions usuallycomprises a thickening agent, such as methylcellulose, in sufficientconcentration to make the solution sufliciently viscous (about 80 toabout 200 centipoises at 25 C.) and uniformly adherent to the surface tobe brightened.

However, such solutions (particularly those containing methylcelluloseas the thickening agent) as have been developed by the art suiferfrom amajor deficiency. They cannot be mass-produced in large quantities andshipped long distances to various points of use nor can they be storedfor much more than 1 month for the reason that, as heretoforeformulated, the solutions rapidly lose viscosity. This loss in viscositycan be compensated for by initially formulating the solution with asufliciently higher concentration of thickening agent so that, eventhough degradation takes place, the solution will have the desiredviscosity. at a predetermined time of use. However, the raw materialcost of such a solution is sufficiently great as to discourageformulators at V to rinse the solution from the brightened surface. To

alloys. There is a tendency more and more for aircraft to be constructedof both aluminum and magnesium parts. Consequently, this problem ofcorrosion of magnesium surfaces is becoming quite serious. Indeed, theUS. Air Force in Technical Order, No. 1-l-lC-Cleaning of AeronauticalEquipmen has stated that All known brightener agents contain chemicalswhich attack magnesium and therefore the use of brighteners on aircraftusing magnesium necessarily must be curtailed.

Still another deficiency of the prior art aluminum brighteners residesin the fact that they are all in aqueous solution form. Elimination ofwater from the composit-ion until the time of use would result insavings in shipping and handling costs. Elimination of the water doesnot, however, solve the problem of excessive loss in viscosity nor doesit eliminate the liquid form of the brightener since'the strong acidswhich make up the prior art compositions are liquid at the usualtemperature of shipping and storage. Furthermore, I have found thatsubstitution of the strong, liquid acids by water-soluble,

solid acids of equal strength or by solid, hydrolyzable acid salts thatwill produce. acids of equal strength in aqueous solution does notprevent excessive degradation of the methylcellulose in the solidformulation and resultant low viscosity of the aqueous solution preparedat the time and place of use.

'It is therefore a general object of this invention to provide the artwith a dry aluminum brightener composition comprising methylcellulose,which, regardless of its-age, will give, upon addition of water, analuminum brightener solution with a viscosity Within the desired range(about to about 200 centipoises at 25 C.).

It is another object of this invention to develop an aluminum brightenercomposition which is substantially noncorrosive to magnesium andmagnesium alloy surfaces.

Still another specific object of this invention is to develop analuminum brightener composition in solid form, which, regardless of itsage, can be readily dissolved in water in a given proportion and give anaqueous solution having a viscosity within the desired range, which issubstantially noncorrosive to magnesium and magnesium alloy surfaces. 7

These and other objects as may appear as this specification proceeds areachieved by this invention.

' In summary, my invention comprises a dry aluminum brightenercomposition consisting essentially of a finely divided mixture of aboutit) to about 25 Weight percent of a solid, hydrolyzable, acid fluoridesalt selected from the group consisting of alkali metal bifluorides,ammonium bifiuoride and sodium silicofluoride; about 20 to about 50weight percent of a solid, water-soluble, organic acid with anionization constant in the range of about 1X 10- to, about 2 lO about 15to about 30 weight percent of a water-soluble methylcellulose of aviscositytype of about 400 to about 4-900 centipoises; and about 10 toabout 30 weight percent of a water-soluble, acid-stable wetting agent. i

The function of the acid fluoride salt is to provide hydrofluoric acidunder conditions of use. Representative acid fluoride salts are ammoniumacid fluoride, so-

' COMPOSITION A Components Weight 7 Percent Ammonium acid fluorideCitric acid Methylcellulose (Viscosity type-4,000 cps.)Alkylarylpolyether alcohol (Triton X-100) or (Igepal C0630). Ammoniumsulfate H H 99. 9 OOOOO The alkylarylpolyether alcohol identified in theforegoing composition as Triton X-l has already been described. Thepolyether identified as Igepal C0630 is an oxyto 3/1; about 0.8 to about2 weight percent of a methylcellulose of a viscosity type of about 400to about 4000 centipoises; and about 0.5 to about 3 weight percent of anonionic wetting agent. Within these limits of concentration saidcompositions have an initial viscosity in the range of about 80 to about3000' centpoises at 25 C., and a viscosity after 6 months from about 80to about 1500 centipoises at 25 C., and are substantially noncorrosiveto magnesium.

ethylated adduct of nonyl phenol which has an oxyethylene content ofabout 65 weight percent of the total molecule.

To prepare an aluminum brightener solution from Composition A, mix 5parts by weight of Composition A with 95 parts by weight of water. Thiscomposition will be completely in solution in a few minutes, and beready for use. Moreover, the resultant solution will have viscositystability over a long period of time.

It has been observed that Composition A in aqueous solution at C. at 5weight percent concentration results in a solution viscosity ofapproximately 200 centipoises, at 7 weight percent a solution viscosityof about 600 centipoises and at 12 Weight percent a solution viscosityof about 5 centipoises. Below the 12 weight percent concentration theacid concentration of the solu- :tion is at a safe level, whereas, above12 weight percent, '.the acid concentration of the solution is such asto re- :sult in excessive etching of aluminum-surfaces. Keeping :in mindthat the desired range of viscosities for alumi- :num brighteners underuse conditions is about 80 to about 200 centipoises, it will be seenthat Composition A has an inherent safety feature in that at unsafeconcentrations the resultant solution is too thin to be used. Thisfeature or property is possessed by all of the compositions of thisinvention.

It has also been observed that when the dry compositions of thisinvention are placed into aqueous solutions and stored for long periodsof time, the solutions display a remarkable degree of viscositystability.

Accordingly, this invention also involves the concept of liquidconcentrates which are prepared by dissolving a solid composition, suchas Composition A, in just enough water to completely solubilize'thecomposition. At the time or place of use the concentrate is then dilutedwith water until the viscosity is in the desired range of about 80 toabout 200 centipoises at which dilution the proportion of solids insolution will be less than about 10 weight percent- In addition, thisinvention involves the concept of liquid, aluminum brightenercompositions that are ready for instant use even after long periods ofstorage.

Such compositions (liquid concentrate and use solution) consistessentially of about 97 to about 87 parts by weight of water and insolution about 0.8 to 8.5

The concentration ranges for the various components of the liquidbrightener composition are established by the same considerations asinvolved in the case of the dry brightener compositions. However, in thecase of the liquid brightener the range of concentrations selected forthe organic acid is somewhat narrower than in the case of the drybrightener. The reason for this is that above the maximum limit organicacids with an ionization constant in the higher end of the ionizationconstant range tend to degrade the methylcellulose in the liquidbrightener over long periods of storage. On the other hand the maximumlimit can be exceeded in the case of organic acids with ionizationconstants in the lower end of the range without accelerating thedegradation of the methylcellulose. Consequently, the concentrationrange set forth is an optimum range generally.

COMPOSITION B Components Weight Percent Ammonium acid fluoride 1. 00Citric a cirl 2. 00 Methylcellulose (Viscosity Type-4,000 cps.) 1.Alkylarylpolyether alcohol (Igepal 00630) 0. 93 EPE nonionic surfactant(Pluronic polyol L64) 0. 92 Water I 93. 30

The alkylarylpolyether alcohol in Composition B has already beendescribed with reference to Composition A. The EPE nonionic surfactantin Composition B is a polyoxyethylene-polyoxypropylene-polyoxyethylenepolyol in which the molecular weight of the polyoxypropylene base is inthe range of about 1500 to about 1800 and the ethylene oxide content ofthe molecule is about 40 weight percent.

A sample ofComposition B has shown an initial viscosity of about 1750centipoises at 25 C. To use Composition B add 1 part by weight of waterto 1 part by weight of Composition B. Such a use solution gave aninitial viscosity of centipoises at 25 C.

Unless otherwise indicated, all viscosity measurements reported in thisspecification were determined at 25 C. with a Brookfield Synchro-LectricViscometer, Model LVF (SN2497) using Spindle No. 2 and speeds of 30r.p,m. ,up to a viscosity of 1000 cps. and 12 r.p.m. for viscositiesover 1000 cps.

To use the aluminum brightener solutions of this'invention, thesolutions in the desired range of viscosity are merely brushed orsprayed on the surface to be brightened The viscous solution remains inplace and will eventually-dry in place unless removed. About 30 secondsafter applying the brightener solution, brightening action as evidencedby gas formation can be observed. After about 5 to 20 minutes, dependingupon the condition of the oxidized aluminum surface, the brighteningcomposition can be removed therefrom by rinsing the surface with waterunder pressure from hoses, sprayers and the like.

' Phosphoric acid 6.5

Viscosity of sciatic .7 Example I This example illustrates the storagestability of the solid compositions of this invention.

A solidjfinely' divided, composition corresponding to Composition A(using Triton X-lOO nonionic) was pro:

pared and stored for approximately a month and a half at 100 Fl atnormal humidity. A weight percent aqueous solution of a sample of thecomposition at the time of preparation gave a viscosity measurement of180 centipoises at room temperature. A 5. weight percent aqueoussolution of a sample of the composition taken at the end of the storageperiod gave a viscosity measurement of 130 centipoises at roomtemperature.

Example 11 To illustrate the viscosity stability of the solutioncompositions of this invention various aluminum brightener compositionconcentrates were prepared and viscosity measurements made. Thefollowing tabulated data was obtained.

TABLE I Weight Percent Components No. 1 No.2 No. 3 No. 4 No.5

Methylcellulose (Viscosity Type -4,000 cps.) Alkylarylpolyether alcohol(Triton X-lGO) 1. 0 1.0 EPE nonionic surfactant (Plur- 'onic nonionioL64) 1.0 1. 0

Ammonium acid fluoride V 1.0 Citric acid. r

Watch"; I"

Viscosity of fresh solution (centipoises at25 C;) 1 "2,000 2,000" '2,000

after at 100 F. (centipoises at 25 (1.). i 700 l 105 230 345 v .975Viscosity of solution after 30 days at 100 F. (centipoises at 25 C.) 27535 60 620 ,pH 01 an aqueous solution with 5% by weight of formulationaiter 9 V days 0.4 2. 5 2.8 f *3 4.5

In the table it will be observed that the best viscosity stability isdemonstrated 'by formulation No. 5, which is the only one within theconcepts of this invention, and that the reduction of viscosity informulation No. 5 is reasonably close to that of the controlformulationNo. 1 comprising methylcellulose and no acid constituents. Just why theviscosity of the control formulation No. 1' oe- V so came reduced is notknown although it is speculated that bacterial action was involved. 7However, the data does demonstrate that the presence of the strong acidsin formulatiOns Nos. 2, 3 and "4 accelerated the reduction 7 inviscosity. v

Example I II This example illustrates the utility of'the compositions ofthis invention. 1 a

The solution composition corresponding to formulation No.-5'-in'-Example II zwas 'diluted on a 1 to 1 weight basis with water and thenapplied to 3 tarnished panels of aluminum alloy (2O24-'1"-3; Alclad)which were disposed in a verticalposition. 'In-each case, after'aboutsecends, the action of the brightener could be seen by the gassingthatoccurred atthe surface of the aluminum alloy.

' Five minutes after placing the brightener composition on V the panels,the-composition was washed oil from each of the panelsunder a stream ofwater and the condition of each of theexposed surfaces was observed. Ineachcase,

' the exposed surface of the pa'nelwas bright, no streak marks wereobserved, and no evidences of white deposits f0! corrosive pittingwereto be found.

8 Example} This invention illustrates thesubstantially non-corrosive;action of the compositions of this invention on magnesium in each case,the panels were removed, rinsed, dried andweighed. The weight changeswere minus 0.080'gram and minus 0.040 gram, respectively. a

Thus it can be seen that in accordance with the con-, cepts of thisinvention aluminum brightener compositions are obtained which not onlyhave the property of good viscosity stability over long periods of time,but which are substantially non-corrosive to magnesium and magnesiumalloys.

Example V This example illustrates the efiect of the ionization constantof the organic acid on the storage stability of the brightenercompositions of this invention. It also illustrates that sodiumbifiuoride may be used in place of ammonium bifiuoride in'thecomposition.

TABLE H Weight Percent Components No. 6 No.7 No. 8

Methylcellulose (Viscosity Type-4,000 cps.) 20 -20 Ammonium Sulfate I40' 40 Alkylarylpolyether alcohol (Triton X-100) Y 10 7 10 AmmoniumBifluoride Sodium Bifluoride 10 Citric Acid 1 7 201.0 Sulfamlc Acid i H20 Viscosity of 5% by weight aqueous solution of sample of formulationwhen first made up (cps. 190 .190 170 Viscosity of 5% by'weight aqueoussolution of sample of formulation after holding for 30 days at-100 F. atnormal humidity (cps.) 155' p, 150 30 Citric acid has a first hydrogenionization constant of 8.7 10- whereas'sulfamic acid has anionizationconstant of 1.01 -l0- It willbe observed that the sulfamicacid formulation (No. 8) is not at all stable in storage as compared tothe citric acid formulations.v

" Example Vl This example illustrates theistorage stability of otherorganic acids having ionization constants within-the range of about 1X10* to about 2X 10- "TABLE, III

. Weight Percent Oomponents No. 9' Noi q No.11

Methylcellulose (Viscosity T e4,ooo ops.) 2'0 20 20 Ammo i fate 40 i0 40Amino 'i ie '10 10 l0 'Alk alcohol (Igepal CO630) .10 Y 10 10 JGlycollio "c d Citric Acii Diglycolliencii Viscosity of 5% byweiglit'aqueous solution of a sample of formulation after storage forapproximately 5 Weeks at 100 F. at normal humidity 120, V 100 Glycollicacid has an ionization constant offLSZXlO,

9 citric acid has an ionization constant for the first hydrogen of 8.7while diglycollic acid has an ionization constant for the first hydrogenof 1.1 X lO- Thus, Within the critical range of ionization constants,the solid, finely divided compositions of this invention have storagestability.

It should be understood that as this invention may be embodied inseveral forms without departing from the spirit or essentialcharacteristics thereof, the embodiments described in this specificationare therefore illustrative and not restrictive, since the scope of theinvention is defined by the appended claims rather than by thedescription preceding them, and all changes that fall within the metesand bounds of the claims, or that form their functional as well asconjointly cooperative equivalents, are therefore intended to beembraced by those claims.

Also, the term consisting essentially of as used in the definition ofingredients present in the composition or compositions claimed isintended to exclude the presence of significant amounts of othermaterials in such proportions as to interfere substantially with theproperties and characteristics possessed by the compositions set forthwhile permitting the presence of other materials in such proportions asnot substantially to affect adversely said properties andcharacteristics.

What is claimed is:

1. A finely divided composition suitable for use in aqueous solution ata concentration of about 2.8 to about 9.5 weight percent to brightenaluminum surfaces which consists essentially of (1) about 10 to about 25weight percent of hydrolyzable acid fluoride salt selected from thegroup consisting of alkali metal bifluorides, arnmonium bifluoride,sodium silicofluoride and mixtures thereof; (2) about 20 to 50 weightpercent of watersoluble organic acid with an ionization constant in therange of about 1X10- up to about 2 l0- (3) about to about 30 weightpercent of water-soluble methylcellulose of a viscosity type of about400 to about 4000 centipoises; and (4) about 10 to about 30 weightpercent of a water-soluble, acid-stable wetting agent.

2. A composition according to claim 1 wherein said organic acid iscitric acid.

3. A composition according to claim 1 wherein said organic acid istartaric acid.

4. A composition according to claim 1 wherein said organic acid isglycollic acid.

5. A composition according to claim 1 wherein said organic acid isdiglycollic acid.

6. A composition according to claim 1 wherein up to about 40 weightpercent of said composition constitutes a. dispersing agentsubstantially free of chlorides, bromides, iodides and strong acids.

7. A composition according to claim 6 wherein said dispersing agentcomprises sugar.

8. A composition according to claim 6 wherein said dispersing agentcomprises urea.

9. A composition according to claim 6 wherein said dispersing agentcomprises ammonium sulfate.

10. A composition suitable for use in aqueous solution at aconcentration of about 5 parts by weight per 95 parts by weight ofwater, which consists essentially of about 10% by weight of ammoniumacid fluoride, about by weight of citric acid, about 20% by weight ofmethylcellulose of viscosity type of about 4000 centipoises, about 10%by weight of a water-soluble, acidstable wetting agent, and about 40% byweight of ammonium sulfate.

11. An aluminum brightener composition consisting essentially of about97 to about 87 parts by weight of water and in solution (1) about 0.8 toabout 8.5 parts by weight of acidic components consisting of ahydrolyzable acid fluoride salt selected from the group consisting ofalkali metal bifiuorides and ammonium bifluorides, and an organic acidwith an ionization constant in the range from about 1 10- to about 2x10-and at a mol ratio to said fluoride salt in a range from about 0.5 toabout 3; (2) about 0.8 to about 2 parts by weight of methylcellulose ofa viscosity type of about 400 to about 4000 centipoises; and (3) about0.5 to about 3 parts by weight of a water-soluble, acid-stable wettingagent, which composition is characterized by a viscosity in the range ofabout 80 to about 3000 centipoises at 25 C.

12. A composition according to claim 11 wherein said organic acid iscitric acid.

13. A composition according to claim 11 wherein said organic acid istartaric acid.

14. A composition according to claim 11 wherein said organic acid isglycollic acid.

15. A composition according to claim 11 wherein said organic acid isdiglycollic acid.

16. An aluminum br-ightener concentrate suitable for use upon dilutionat a 1 to 1 weight ratio with water, which consists essentially of about93 weight percent of water and in solution (1) about one weight percentof ammonium acid fluoride; (2) about two weight percent of citric acid;(3) about two weight percent of methylcellulose of a viscosity type ofabout 4000 centipoises; (4) about one weight percent of analkylarylpolyether alcohol wetting agent; and (5) about one weightpercent of a polyoxyethylene-polyoxypropylene-polyoxyethylene nonionicwherein the polyoxypropylene portion of the molecule has a molecularweight in the range of about 800 to about 2500 and wherein thepolyoxyethylene oxide content of the total molecule is to weightpercent.

17. A method for brightening a tarnished aluminum surface in conjunctionwith a magnesium surface wherein the magnesium surface isnot'substantially damaged, which comprises (1) applying to said surfacea viscous liquid consisting essentially of about 97.2 to about 90.5weight percent of water and in solution about 2.8 to about 9.5weightpercent of a composition consisting essentially of about 10 toabout 25 weight percent of a hydrolyzable, acid fluoride salt selectedfrom the group consisting of alkali metal bifluoride, ammoniumbifiuoride, sodium silicofluoride and mixtures thereof, about 20 toabout 50 weight percent of an organic acid with an ionization constantin the range of about 1X10" to about 2 10'- about 15 to about 30 weightpercent of a methylcellulose of a viscosity type of about 400 to about4000 centipoises, and about 10 to about 30 weight percent of awater-soluble, acid-stable wetting agent, said liquid having a viscosityin the range of about 80 to about 200 centipoises at 25 C.; and (2)rinsing said solution from said surface when the tarnish on said surfacehas been removed therefrom.

18. A method according to claim 17 wherein the mol ratio of said organicacid to said fluoride salt is in a range of about 0.5/1 to 3/1.

References Cited in the file of this patent UNITED STATES PATENTS2,687,346 McDonald Aug. 24, 1954

1. A FINELY DIVIDED COMPOSITION SUITABLE FOR USE IN AQUEOUS SOLUTION AT A CONCENTRATION OF ABOUT 2.8 TO ABOUT 9.5 WEIGHT PERCENT TO BRIGHTEN ALUMINUM SURFACES WHICH CONSISTS ESSENTIALLY OF (1) ABOUT 10 TO ABOUT 25 WEIGHT PERCENT OF HYDROLYZABLE ACID FLUORIDE SALT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL BIFLUORIDES, AMMONIUM BIFLUORIDE, SODIUM SILICOFLUORIDE AND MIXTURES THEREOF, (2) ABOUT 20 TO 50 WEIGHT PERCENT OF WATERSOLUBLE ORGANIC ACID WITH AN IONIZATION CONSTANT IN THE RANGE OF ABOUT 1X10**-4 UP TO ABOUT 2X10**-3, (3) ABOUT 15 TO ABOUT 30 WEIGHT PERCENT OF WATER-SOLUBLE METHYLCELLULOSE OF A VISCOSITY TYPE OF ABOUT 400 TTO ABOUT 4000 CENTIPOISES, AND (4) ABOUT 10 ABOUT 30 WEIGHT PERCENT OF A WATER-SOLUBLE, ACID-STABLE WETTING AGENT. 